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The main reasons for modifying a concept in an extension are:

  • The concept is marked as fully defined, but should be primitive
  • The concept is marked as primitive, but has now been fully defined
  • The concept is inactive but needs to be reactivated
  • The concept is active, but needs to be inactivated (Note - This scenario is described further in Inactivate Description in an Extension.)

If an extension producer needs to modify the definition of a concept, this will necessitate adding, modifying or inactivating the relationships for which the given concept is the source. For more information, please refer to 5.4.4 Authoring Relationships.

If an extension producer needs to modify the terms used to describe the concept, this will necessitate adding, modifying or inactivating the descriptions associated with the concept. For more information, please refer to 5.4.3 Authoring Descriptions.



The clinical meaning of each concept in SNOMED CT is permanent, and can not be modified over time. This clinical meaning is captured by the concept's Fully Specified Name. Changing the clinical meaning of a concept therefore requires inactivating the concept, and creating a new concept that represents the new meaning.

The following changes, however, are permitted: 

  • Modifying mutable attribute values, such as definitionStatusId.
  • Adding, modifying or inactivating descriptions, including changing the concept's Fully Specified Name to conform to editorial policy (as long as there is no change in clinical meaning). Please refer to 5.4.3 Authoring Descriptions.
  • Changing the way that a clinical meaning is formally defined. This can be done by adding, modifying or inactivating the concept's defining relationships and/or changing the definition status of the concept. Please refer to 5.4.4 Authoring Relationships.

Modifying Mutable Attribute Values 

The attributes of a concept may be modified, as long as the change is limited to the values of its mutable attributes. The values of immutable attributes should never be modified.

The effectiveTime attribute is used to support the versioning of each concept. Permitted concept modifications therefore include: 

  • active: Changing the concept's active attribute from active to inactive, or from inactive to active.
  • definitionStatusId: Changing the concept's definition status from primitive to fully defined, or from fully defined to primitive.
  • moduleId: Changing the concept's module. For example, this may occur when a concept is promoted. Please refer to Promotion and Demotion.

It should be noted that extensions should not modify the attributes of an international concept, unless this modification is necessary to meet legitimate clinical needs or to correct identified clinical issues. Any new version of an international concept that is created by an extension producer (other than SNOMED International) and which modifies the concept's mutable attributes, should be:

  • Assigned to an extension module (and not an international module) to reflect the fact that the modification was not made by SNOMED International.
  • Submitted to SNOMED International with an explanation as to why the change was necessary.


The table below provides a summary of the process to follow when modifying a concept in an extension.

File TypeProcess

A new row, which represents the new version of the concept, is added to the concept file.

The attributes of the new version of the concept are set as follows:

  • id is set to the conceptId of the concept being modified
  • effectiveTime is set to the date the extension will be published
  • active is set to indicate whether or not the concept is active at the given effective time ('1' for active and '0' for inactive)
  • moduleId is set to the conceptId of a module that is managed by the extension producer
  • definitionStatusId is set to indicate whether the concept is primitive or fully defined

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